Wang J, Oruganti B, Durbeej B. Computational Comparison of Chemical and Isotopic Approaches to Control the Photoisomerization Dynamics of Light-Driven Molecular Motors.
J Org Chem 2021;
86:5552-5559. [PMID:
33784457 PMCID:
PMC8154570 DOI:
10.1021/acs.joc.1c00063]
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Abstract
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Synthetic molecular
motors driven by E/Z photoisomerization
reactions are able to produce unidirectional
rotary motion because of a structural asymmetry that makes one direction
of rotation more probable than the other. In most such motors, this
asymmetry is realized through the incorporation of a chemically asymmetric
carbon atom. Here, we present molecular dynamics simulations based
on multiconfigurational quantum chemistry to investigate whether the
merits of this approach can be equaled by an alternative approach
that instead exploits isotopic chirality. By first considering an N-methylpyrrolidine–cyclopentadiene motor design,
it is shown that isotopically chiral variants of this design undergo
faster photoisomerizations than a chemically chiral counterpart, while
maintaining rotary photoisomerization quantum yields of similarly
high magnitude. However, by subsequently considering a pyrrolinium–cyclopentene
design, it is also found that the introduction of isotopic chirality
does not provide any control of the directionality of the photoinduced
rotations within this framework. Taken together, the results highlight
both the potential usefulness of isotopic rather than chemical chirality
for the design of light-driven molecular motors, and the need for
further studies to establish the exact structural circumstances under
which this asymmetry is best exploited.
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